.pagehead
    display block
.widthRatio
    border 1px solid red
@media (device-height: 568px) and (-webkit-min-device-pixel-ratio: 2)   
    .foo 
      margin-left 32%
  
@media (device-height: 667px) and (-webkit-min-device-pixel-ratio: 2) 
/* 兼容iphone6 */
    .foo 
      margin-left 44%
@media (device-height: 736px) and (-webkit-min-device-pixel-ratio: 3) 
/* 兼容iphone6plus */
    .foo 
      margin-left 50%